化合
かごう · kagou · JLPT N1 · noun
combination
化 — person 亻 + spoon/upside-down person 匕
化 is an associative compound showing a standing person 亻 next to 匕, originally a depiction of a person turned upside-down. Together they suggest a figure transforming from one state to another, giving the core meaning 'change' or 'transform'. The character later extended to senses like 'convert', 'influence', and the noun suffix '-ization'.
合 — 乛 (lid/roof) + 口 (mouth)
Originally a pictograph of a lidded vessel — a cover (亼) closing over an opening (口) — giving the core sense of 'come together, join, fit.' From 'fit/match' it extended to 'combine, unite, agree' and to measure-word uses. The reading hé reflects this 'joining' meaning.